The keylog reader used fscanf with three whitespace delimited tokens,
which is not line aware. RFC 9850 Section 1 requires readers to ignore
empty lines and lines whose first character is '#', and Section 2
recommends ignoring lines that do not conform to the format so secrets
can still be recovered from corrupted files. A comment line such as
"# note" was parsed as three fields spanning the line boundary, which
desynchronized the rest of the file.
Read one line at a time with fgets, skip empty and comment lines, and
parse each line with sscanf, skipping any line that does not yield the
three expected fields instead of aborting. Clear the field buffers each
iteration so a short field cannot pick up stale bytes from a previous
line, validate that the fixed length client random field is the exact
expected length, and leave the secret length variable because it depends
on the negotiated hash. Zero the new line buffer on every return path,
matching the existing ForceZero handling of the secret buffers.
Add a comment line, a blank line, and a malformed line to the TLS 1.3
keylog test data so the sniffer keylog test exercises the skip paths.
Tobias Frauenschläger
34a2a2f389